My transfer shudders as I drive my GM truck

GM has issued a TSB (#99-04-1-005A) for 1999-01 Chevrolet and GMC L-Van models and Oldsmobile Bravada equipped with the NV136 transfer case. The symptom is a vibration or “shudder” that occurs during tight turning on dry pavement and at speeds less than 5mph. The problem has been linked to what GM calls “Slip-stick.” That’s where the clutch plates in the transfer case bind and then release. The TSB calls for flushing the transfer case fluid with new Auto-TrakII fluid (blue in color). First drain the transfer case fluid (even if the old fluid is blue in color). Refill with new fluid (part #12378508). Then drive the vehicle a minimum of 5 miles until the transfer case fluid is up to operating temperature. Then drain and refill a SECOND time. GM warns that even after performing this flush and fill procedure, it may take up to 100 miles for the problem to disappear. This isn’t a recall, so you should expect to pay for this repair.

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